1. Field
Disclosed herein is an apparatus and related methods for the continuous fabrication of pre-stressed structural members from a compressible core and a cellulose-based sheet material wrapper.
2. Related Art
Shipping pallets have traditionally been made out of wood. However, the use of wood presents a number of problems. For example, wood pallets may present a hazard to workers or cause damage to the products and materials loaded upon the pallets due to splintering of the wood. The splintered wood can impale both workers and the packaging and products being transported on the pallets. In addition, wood pallets are typically assembled using fasteners such as nails or staples. Such fasteners present additional hazards that may cause injury to workers and damage to the products and packaging being transported on the pallets. Such injuries negatively impact the lives of workers and add delays and costs to product distribution. Accordingly, it would be beneficial to have a pallet that reduced or eliminated such hazards.
Similarly, wood pallets typically weigh between 40 and 65 pounds. As such, wood pallets may be cumbersome for individuals to handle even when unloaded. The weight of the pallet may cause injury to workers particularly when being manually stacked or otherwise handled after unloading. The weight also adds to shipping costs and may create other inefficiencies. For example, a trailer that is 53 feet long with a double-stacked load can include 52 pallets, which typically adds over 2500 pounds of weight per truck load. With lighter the goods, such as, for example, aluminum cans, a lighter pallet can dramatically affect the total weight of the load because of the greater proportion of weight of the wood pallets in the load relative to the goods. With heavier goods that won't permit the total volume of a trailer to be utilized because of weight restrictions, a lighter pallet will permit additional goods to be transported of light palletized loads. Regardless of the load, the weight of the traditional pallets represents a significant addition cost to shipping goods. Accordingly, it would be beneficial to have a pallet that minimized the additional weight associated with palletizing goods.
In addition, the wood used for pallets has a significant impact on the environment. The wood pallet industry currently consumes over 1 million acres of forest per year for the manufacture of new wood pallets. Depletion of natural resources, destruction of animal habitat and excessive use of energy are the obvious impacts of such harvesting. In addition, the harvested wood may be the carrier of potentially invasive species. Given that pallets are used for shipping, pallets have been implicated in the dissemination of potentially invasive species around the world. In order to prevent the importation of invasive species, certain countries are currently implementing restrictions on wood pallets or are totally banning the use of wood pallets. These restrictions may require the use of fumigation or heat-treating to kill invasive species harbored in the wood. However, these restrictions may add to the cost, environmental impact, and disposal problems associated with the use of such wood pallets. Accordingly, it may be mandatory or at least beneficial to use pallets that reduced or eliminated the need to harvest and transport wood.
Corrugated pallets fabricated from corrugated materials or other paper products represent solutions to many of the above listed problems. However many current corrugated pallets may lack the strength to be competitive with wood pallets, may be vulnerable to water damage, and may be prohibitively expensive. In addition, corrugated pallets may have unconventional configurations that may confuse forklift operators resulting in additional damage, and that may not be usable with existing storage rack systems and existing conveyor systems commonly used in manufacturing and warehousing facilities. These shortcomings may present a barrier to the widespread usage and acceptance of corrugated pallets.
Certain corrugated pallet designs have overcome many of these problems using a paper wrapper bonded to corrugated cores to form planks for fabrication of the corrugated pallet. It has been further shown that it can be advantageous to bond the paper wrapper in tension to the core. The tension may be selectable in order to impart desired structural properties to the plank. However, the manufacture of such planks with tensioned paper wrappers disposed over corrugated cores presents a number of manufacturing problems. In order to cost effectively manufacture the planks, a paper wrapper should be secured to the core surface of the core at a rapid rate. Many prior technologies for wrapping a paper wrapper over a cardboard core did not secure the paper wrapper in tension over the cardboard core. In addition, the prior technologies for wrapping paper around cores were typically too slow and expensive for efficient manufacture of planks.
Various prior plastic wrapping technologies used plastic wrappers that were highly elastic and relied on this high degree of elasticity and, typically, multiple wraps around the core to secure the wrapper over the core. These plastic-wrapping technologies did not actually bond the plastic wrapper to the cellulose-based core. The nature of the materials typically prevented this. Accordingly, the plastic was typically adhered to itself around the cores to secure the plastic wrapper about the core. This technology didn't bond the plastic to the surface of the cores to provide the additional strength advantage of the wrapper bonded to the core. Furthermore, the underlying technology was not directly or readily adaptable for use with paper due to the different physical nature of paper and other similar cellulose based sheet materials.
The limited elasticity of paper and the need to use adhesives to bond the paper wrapper directly to the core particularly present a number of distinct problems that will be readily recognized by those of ordinary skill in the art and are not resolved by prior wrapping technologies. Accordingly, it would be beneficial to have a manufacturing apparatus for the efficient and cost effective bonding of paper wrappers around cardboard cores.